Dye imbibition imaging

ABSTRACT

PROCESS OF FORMING DYE-IMBIBITION IMAGES WHEREIN POWDER PARTICLES COMPRISING A DYE, HELD IN IMAGE-WISE CONFIGURATION IN PARTICULATE FORM IN OR ON A SUBSTRATE, IS CONTACTED WITH VAPORS OF A MATERIAL, WHICH IS A SOLVENT FOR SAID DYE AND CAPABLE OF SWELLING THE SURFACE OF SAID SUBSTRATE, MOLECULARLY IMBIBING SAID DYE INTO SAID SUBSTRATE. LINE, CONTINUOUS-TONE OR HALF-TONE IMAGES ARE PREFERABLY PRODUCED BY EXPOSING TO ACTINIC RADIATION IN IMAGERECEIVING MANNER A SUBSTRATE BEARING A POSITIVE-ACTING OR NEGATIVE-ACTING LIGHT-SENSITIVE ORGANIC LAYER HAVING A THICKNESS OF AT LEAST 0.1 MICRON, SAID LAYER BEING CAPABLE OF DEVELOPING A RD OF 0.2 TO 2.2 CONTINUING THE EXPOSURE TO EITHER CLEAR THE BACKGROUND OF POSITIVE-ACTING LIGHT-SENSITIVE LAYERS OR TO ESTABLISH A POTENTIAL RD OF 0.2 TO 2.2 WITH NEGATIVE-ACTING LIGHT-SENSITIVE ORGANIC LAYERS; APPLYING TO SAID LAYER OF ORGANIC METERIAL, FREE FLOWING POWDER PARTICLES HAVING A DIAMETER, ALONG AT LEAST ONE AXIS OF AT LEAST 0.3 MICRON BUT LESS THAN 25 TIMES THE THICKNESS OF SAID ORGANIC LAYER WHEREIN SAID POWDER PARTICLES COMPRISE A SOLID CARRIER AND DYE; WHILE THE LAYER IS AT A TEMPERATURE BELOW THE MELTING POINTS OF THE POWDER AND OF THE ORGANIC LAYER, PHYSICALLY EMBEDDING SAID POWDER PARTICLES AS A MONOLAYER IN A STRATUM AT THE SURFACE OF SAID LIGHT-SENSITIVE LAYER TO YIELD IMAGES HAVING PORTIONS VARYING IN DENSITY IN PROPORTION TO THE LIGHT EXPOSURE OF EACH PORTION, REMOVING NON-EMBEDDED PARTICLES FROM SAID ORGANIC LAYER TO DEVELOP AN IMAGE; AND MOLECULARLY IMBIBING DYE INTO THE SUBSTRATE (INCLUDING SUBBING LAYER ON SAID SUBSTRATE) BY CONTACTING THE PARTICLES EMBEDDED IN SAID ORGANIC LAYER WITH VAPORS OF A MATERIAL WHICH IS A SOLVENT FOR SAID DYE AND CAPABLE OF SWELLING SAID SUBSTRATE.

United States Patent U.S. C]. 96-48 24 Claims ABSTRACT OF THE DISCLOSURE Process of forming dye-imbibition images wherein powder particles comprising a dye, held in image-wise configuration in particulate form in or on a substrate, is contacted with vapors of a material, which is a solvent for said dye and capable of swelling the surface of said substrate, molecularly imibi'bing said dye into said substrate. Line, continuous-tone or half-tone images are preferably produced by exposing to actinic radiation in imagereceiving manner a substrate bearing a positive-acting or negative-acting light-sensitive organic layer having a thickness of at least 0.1 micron, said layer being capable of developing a R of 0.2 to 2.2; continuing the exposure to either clear the background of positive-acting light-sensitive layers or to establish a potential R of 0.2 to 2.2 with negative-acting light-sensitive organic layers; applying to said layer of organic material, free flowing powder'particles having a diameter, along at least one axis of at least 0.3 micron but less than 25 times the thickness of said organic layer wheren said powder particles comprise a solid carrier and dye; while the layer is at a temperature below the melting points of the powder and of the organic layer, physically embedding said powder particles as a monolayer in a stratum at the surface of said light-sensitive layer to yield images having portions varying in density in proportion to the light exposure of each portion, removing non-embedded particles from said organic layer to develop an image; and molecularly imbibing dye into the substrate (including subbing layer on said substrate) by contacting the particles embedded in said organic layer with vapors of a material which is a solvent for said dye and capable of swelling said substrate.

This application is a continuation-in-part of application Ser. No. 796,897, filed Feb. 5, 1969, now abandoned.

This invention relates to a method of forming dye imbibition images wherein powder particles comprising a dye, held in image-wise configuration in particulate form in or on a substrate, is contacted with vapors of a material, which is a solvent for said dye and capable of swelling the surface of said substrate molecularly imbibing said dye into said substrate. More particularly, this invention relates to a method of forming direct-reading, positive, continuous-tone, dye imbibition deformation images without forming a negative intermediate, wherein the continuous tone deformation image is developed by mechanically embedding particles comprising a dye into a stratum at the surface of a powder-receptive, solid, light-sensitive organic layer supported on a substrate and molecularly imbibing dye into the substrate in image-wise configuration by contacting the particles embedded in said organic layer with vapors of a material which is a solvent for said dye and capable of swelling said substrate.

Although numerous photographic reproduction processes utilizing a wide variety of sensitizers have 'been developed, conventional continuous tone black and white or color reproductions are produced with silver halide emulsions. When compared to other light-sensitive systerns, silver halide emulsions can be developed to provide continuous tone images by well established practical techniques. However, silver halide emulsions generally are negative-acting and" are developing either by diffusion transfer or in suitable chemical baths to produce a negative, followed by printing a positive. Accordingly, there is a need for a simple commercial process for forming permanent continuous tone reproductions directly on a lightsensitive element.

There are several photographc processes where a latent image is formed directly in or on a light-sensitive thermoplastic element and developed after converting the thermoplastic portion of the exposed light-sensitive thermoplastic element into a liquid or semi-solid softened state necessary for development. The developed image is made permanent by hardening the liquid or semi-solid thermoplastic material. These techniques are used in plastic deformation imaging where at latent image is formed by exposure to actinic radiation and developed by the application of a suitable force. For example, image development can result from the production of discontinuities on the surface of a thremoplastic light-sensitive element, such as frost pattern or rippled images in xerography, or within the thermoplastic light-sensitive element, such as gas bubbles in vesicular prints. The discontinuities in the frost deformation images scatter light and become visible when subjected to transmitted light, preferably provided by an optical viewer or projector.

In very simplified form, prior art deformation imaging processes employ a light exposure step followed by temporary softening of the thermoplastic layer by heat or solvent, which permits a suitable force, such as electrostatic or gas pressure, to deform the thermoplastic light-sensitive element. The images or discontinuities are frozen into or on the thermoplastic layer by hardening said layer, usually by cooling the melted layer. U.S. Pat. No. 3,317,315 indicates that xerographic deformation proceses have the advantage, when compared to conventional xerographic processes, that they do not require means for applying toner or means for fixing the toner to form a permanent image. However, light scattering deformation imaging processes have the obvious drawback that they require a softening step, usually heating, and yield images that lack the black-white contrast demanded by the public for viewing with the naked eye. In some cases, frost patterns can be produced without a temporary softening step by suitable choice of thermoplastic material, but the images lack permanence.

U.S. Pat. 3,060,024 discloses forming a latent image by exposing a thermoplastic light-sensitive element comprising a thermoplastic polymer and a plasticizing addition polymerizable monomer to light until substantial polymerization takes place in the exposed areas. The latent image is developed by heating the light-sensitive element to soften or liquefy the underexposed thermoplastic areas, dusting or sprinkling the element with a suitable powder, such as carbon black, cooling the light-sensitive element to freeze the particles into the underexposed areas and removing unattached powder from the non-image areas. The patentees indicate that this process is suitable for the production of line images or half tone reproductions.

U.S. Pat. 2,090,450 disclose that acetals of nitrobenzaldehydes can be changed by exposure to light to render the exposed area either adhesive or non-adhesive. The exposed element is developed by dusting with a suitable powder, such as soot.

The general object of this invention is to provide a method for forming dye imbibition images wherein powder particles comprising a dye held in image-wise configuration in particulate form in or on a substrate is contacted with vapors of a material, which is a solvent for said dye and capable of swelling the surface of said substrate, molecularly imbibing said dye into said substrate. One important object of this invention is to provide a method of forming direct-reading, positive, continuoustone dye imbibition deformation images without forming a negative intermediate. Other objects will become apparent below.

In the description that follows, the phrase powderreceptive, solid, light-sensitive organic layer is used to describe an organic layer which is capable of developmg a predetermined contrast or reflection density (R upon exposure to actinic light and embodiment of black powder particles of a predetermined size in a single stratum at the surface of said organic layer. While explained in greater detail below, the R of a light-sensitive layer is a photometric measurement of the difference in degree of blackness of undeveloped areas and black powder developed areas. The terms physically embedded or physical force are used to indicate that the powder particle is subjected to an external force other than, or in addition to, either electrostatic force or gravitational force resulting from dusting or sprinkling powder particles on a substrate. The terms mechanically embedded or mechanical force are used to indicate that the powder particle is subjected to a manual or machine force, such as a lateral to-and-fro or circular rubbing or scrubbing action. The term embedded is used to indicate that the powder particle displaces at least a portion of the light-sensitive layer and is held in the depression so created, i.e. at least a portion of each particle is below the surface of the lightsensitive layer.

The present invention provides a method of forming dye imbibition images, preferably dye imbibition deformation images, wherein powder particles comprising a dye, held in image-wise configuration in particulate form in or on a substrate, is contacted with vapors of a material which is a solvent for said dye and capable of swelling the surface of said substrate, molecularly imbibing said dye into said substrate, thereby increasing the saturation of the dye image. Preferably, the powder particles comprising a dye, held in image-wise configuration in particulate form are deposited by the deformation imaging process described and claimed in copending application Ser. No. 796,847, filed on even date in the name of Hayes, Jones and Thompson. In order to facilitate a complete understanding of the present invention, there is also disclosed the various parameters necessary for obtaining deformation images in accordance with Ser. No. 796,847 and the further modifications of said process necessary to obtain dye imbibition deformation imaging.

In its preferred aspect, this invention makes use of the discoveries that (1) thin layers of many solid organic materials, some in substantially their naturally occurring or manufactured forms and others, including additives to control their powder receptivity and/or sensitivity to actinic radiation, can have surface properties than can be varied within a critical range by exposure to actinic radiation between a particle-receptive condition and a particle-non-receptive condition such that, by the methods of the present invention, continuous-tone images of high quality can be formed as wel as line images and half-tones and (2) if said particle comprises a dye, the dye can be imbibed into a substrate for said thin layer by treating the thin layer with vapors of a material which is a solvent for the dye and a swelling agent for the thin layer. As explained below, the particle receptivity and particle nonreceptivity of the solid thin layers are dependent on the size of the particles, the thickness of the solid thin layer and the development conditions, such as layer temperature.

Broadly speaking, the deformation imaging aspect of the present invention differs from known processes in various subtle and unobvious ways. For example, the particles that form an image are not merely dusted on, but instead are applied against the surface of the lightsensitive thin layer under moderate physical force. The relatively soft or particle-receptive nature of the lightsensitive layer is such that substantially a monolayer of particles, or isolated small agglomerates of a predetermined size, are at least partially embedded in a stratum at the surface of the light-sensitive layer by moderate physical force. The surface condition in the particle-receptive areas is at most only slightly soft but not fluid, as in prior processes. The relatively hard or particle-non-receptive condition of the light-sensitive surface in the nonimage areas is such that when particles of a predetermined size are applied under the same moderate physical force few, if any, are embedded sufiiciently to resist removal by moderate dislodging action such as blowing air against the surface.

The ease with' which continuous tone deformation images are produced by the process of this invention is significant. In various preferred forms of this invention, the light-sensitive organic layer is sensitized to actinic radiation in such manner that a determinable quantity of actinic radiation changes the surface of the film from the particle receptive condition to the non-receptive condition. The unexposed areas accept a maximum concentration of particles while fully exposed areas accept no particles. In others, the light-sensitive organic layer is sensitive to actinic radiation in the opposite way, such that a determinable quantity of such radiation changes the surface of the film from the particle non-receptive condition to the receptive condition. In both types of layers, the sensitivity typically is such that smaller quantities of actinic radiation provide proportionately smaller changes in the surface of the layer to provide a continuous range of particle receptive conditions between fully receptive and non-receptive conditions. Thus, the desired image may include intermediate light values, as are typically produced by actinic radiation through a continuous tone transparency. While the continuous nature of images pro duced by the method of this invention cannot be fully explained from a technical standpoint, microscopic studies have established that the range of R (reflection density) obtainable is attributable to the number of particles embedded per unit area. Since only a monolayer of particles is embedded, the light-sensitive layer can be viewed functionally as an ultrafine screen yielding continuous tone images. No such results have been reported in prior powder-imaging methods, even those using some of the same materials but in different modes from those of the present invention. This is probably due to the fact that prior powder-imaging processes rely on electrostatics or liquefaction of the unexposed areas, which lead to the formation of multilayers of powder particles, precluding the formation of continuous tone images.

The quality of the deformation images obtained by the process of this invention is superior to that of prior powder-imaging processes. Line images free of background, having good density and high resolution (beter than 40 line pairs per mm.) are readily obtained. As explained below, half-tone reproductions and continuous-tone images are also provided readily. Images obtainable by the process of this invention compare favorably with silver halide photographs. Full color reproductions of excellent photographic quality, both half-tone and continuous-tone, are provided simply by repeating the basic processes and applying successively suitable powders of cyan, magenta, and yellow hues in any sequence. Black may be added where desired for further detail. Each developed lightsensitive layer can form the substrate for the next lightsensitive layer and particles of a different color can be applied against the surface of each layer.

For use in this invention, the solid, light-sensitive organic layer, which can be an organic material in its naturally occurring or manufactured form or a mixture of said organic material with plasticizers and/or photoactivators for adjusting the powder receptivity and sensitivity to actinic radiation, must be capable of developing a predetermined contrast or R using a suitable black developing powder under the conditions of development. The powder-receptive areas of the layer (unexposed areas of a positive-acting, light-sensitive material or the exposed areas of a negative-acting, light-sensitive material) must have a softness such that suitable particles can be embedded into a stratum at the surface of the lightsensitive layer by mild physical forces. However, the layer should be sufliciently hard and non-sticky that film transparencies can be pressed against the surface, as in a vacuum frame, without the surfaces sticking together or being damaged even when heated slightly under high intensity light radiation. The film should also have a degree of toughness so that it maintains its integrity during development. If the R of the light-sensitive layer is below about 0.2, the light-sensitive layer is too hard to accept a suitable concentration of powder particles. On the other hand, if the R is above about 2.2, the light-sensitive layer is so soft that it is difficult to maintain film integrity during physical development and the layer tends to adhere to transparencies precluding the use of vacuum frame exposure equipment. Further, if the R is above 2.2, the light-sensitive layer is so soft that more than one layer of powder particles may be deposited with attendant loss of continuous-tone quality and image fidelity and the layer may be displaced by mechanical forces resulting in distortion or destruction of the image. Accordingly, for use in this invention the light-sensitive layer must be capable of developing a R within the range of 0.2 to 2.2 or preferably 0.4 to 2.0 using a suitable black developing powder under the conditions of development.

The R of a positive acting light-sensitive layer, which is called R is a photometric measurement of the reflection density of a black-powder developed light-sensitive layer after a positive-acting, light-sensitive layer has been exposed to sufficient actinic radiation to convert the exposed areas (or most exposed areas, When a continuoustone transparency is used) into a substantially powdernon-receptive state (clear the background). The R of a negative-acting light-sensitive layer, which is called R is a photometric measurement of the reflection density of a black powder developed area, after a negativeacting, light-sensitive layer has been exposed to suflicient actinic radiation to convert the exposed area into a powder-receptive area.

In somewhat greater detail, the reflection density of a solid, positive-acting, light-sensitive layer (R is determined by coating the light-sensitive layer on a white substrate, exposing the light-sensitive layer to suflicient actinic radiation imagewise to clear the background of the solid positive-acting, light-sensitive layer, applying a black powder (prepared from 77% Pliolite VTL and 23% Neo Spectra carbon black in the maner described below) to the exposed layer, physically embedding said black powder under the conditions of development as a monolayer in a stratum at the surface of said light-sensitive layer and removing the non-embedded particles from said light-sensitive layer. The developed organic layer containing black powder embedded image areas and substantially powder free non-image areas is placed in a standard photometer having a scale reading from to 100% reflection of incident light or an equivalent density scale, such as on Model 500A photometer of the Photovolt Corporation. The instrument is zeroed (0 density; 100% reflectance) on a powder free non-image area of the light-sensitive organic layer and an average R reading is determined from the powder developed area of line and half-tone images. With continuous-tone images the R reading is determined on the blackest powder developed area. The reflection density is a measure of the degree of blackness of the developed surface which is relatable to the concentration of particles per unit area. The reflection density of a solid, negative-acting lightsensitive layer (R is determined in the same manner except that the negative-acting light-sensitive layer is exposed to sufficient actinic radiation to convert the exposed area into a powder receptive area. If the R under the conditions of development is between 0.2 (63.1% reflectance) and 2.2 (0.63% reflectance), or preferably between 0.4 (39.8% reflectance) and 2.0 (1.0% reflectance), the solid, light-sensitive organic material deposited in a layer is suitable for use in this invention.

Although the R of all light-sensitive layers is determined by using the aforesaid black developing powder and a white substrate, the R is only a measure of the suitability of a light-sensitive layer for use in this invention.

Since the R of any light-sensitive layer is dependent on numerous factors other than the chemical constitution of the light-sensitive layer, the light-sensitive layer is best defined in terms of its R under the development conditions of intended use. The positive-acting, solid, lightsensitive organic layers useful in this invention must be powder receptive in the sense that the aforesaid black developing powder can be embedded as a mono-particle layer into a stratum at the surface of the unexposed layer to yield a R of 0.2 to 2.2 (0.4 to 2.0 preferably) under the predetermined conditions of development and lightsensitive in the sense that upon exposure to actinic radiation the most exposed areas can be converted into the non-particle receptive state (background cleared) under the predetermined conditions of development. In other words, the positive-acting, light-sensitive layer must contain a certain inherent powder receptivity and light-sensitivity. The positive-acting, light-sensitive layers are apparently converted into the powder-non-receptive state by a light-catalyzed hardening action, such as photopolymeri zation, photocrosslinking, photooxidation, etc. Some of these photohardening reactions are dependent on the presence of oxygen, such as the photooxidation of internally ethylenically unsaturated acids and esters while others are inhibited by the presence of oxygen, such as those based on the photopolymerization of vinylidene or polyvinylidene monomers alone or together with polymeric materials. The latter require special precautions, such as storage in oxygen-free atmosphere or oxygen-impermeble cover sheets. For this reason, it is preferable to use solid, positive-acting, film-forming, organic materials containing no terminal ethylenic unsaturation.

The negative-acting, solid light-sensitive organic layers useful in this invention must be light-sensitive in the sense that, upon exposure to actinic radiation, the most exposed areas of the light-sensitive layer are converted from a non-powder-receptive state under the predetermined conditions of development to a powder-receptive state under the predetermined conditions of development In other words, the negative-acting light-sensitive layer must have a certain minimum light-sensitivity and potential powder receptivity. The negative-acting light-sensitive layers are apparently converted into the powder receptive state by a light-catalyzed softening action, such as photodepolymerization.

In general, the positive-acting, solid, light-sensitive layers useful in this invention comprise a film-forming organic material in its naturally occurring or manufactured form or a mixture of said organic material with plasticizers and/or photoactivators for adjusting powder receptivity and sensitivity to actinic radiation. Suitable positive-acting, film-forming organic materials, which are not inhibited by oxygen, include internally ethylenically unsaturated acids, such as abietic acid, rosin acids, partially hydrogenated rosin acids, such as those sold under the name Staybelite resin, etc.; esters of internally ethylenically unsaturated acids, methylol amides of maleated oils such as described in application Ser. No. 643,367, filed June 5, 1967, phosphatides of the class described in application Ser. No. 796,841 filed on even date in the name of Hayes now Pat. No. 3,585,031, such as soybean lecithin, partially hydrogenated lecithin, dilinolenyl-alphalecithin, etc.; partially hydrogenated rosin acid esters, such as those sold under the name Staybelite esters, rosin modified alkyds, etc.; polymers of ethylenically unsaturated monomers, such as vinyltoluene-alpha methyl styrene copolymers, polyvinyl cinnamate, polyethyl methacrylate, vinyl acetate-vinyl stearate copolymers, polyvinyl pyrrolidone, etc.; coal tar resins, such as coumaroneindene resins, etc.; halogenated hydrocarbons, such as chlorinated waxes, chlorinated polyethylene, etc. Positive acting, light-sensitive materials, which are inhibited by oxygen include mixtures of polymers, such as polyethylene terephthalate/sebacate, or cellulose acetate or acetate/ butyrate, with polyunsaturated Vinylidene monomers, such as ethylene glycol diacrylate or dimethacrylate, tetraethylene glycol diacrylate or dimethacrylate, etc.

Although numerous positive-acting, film-forming organic materials have the requisite light-sensitivity and powder receptivity at predetermined development temperatures, it is generally preferable to compound the film-forming organic material with photoactivator(s) and/or plasticizer(s) to impart optimum powder receptivity and light-sensitivity to the light-sensitive layer. In most cases, the light-sensitivity of an element can be increased many fold by incorporation of a suitable photoactivator capable of producing free-radicals, which catalyze the light-sensitive reaction and reduce the amount of photons necessary to yield the desired physical change. For example, the near ultraviolet light sensitivity of soybean lecithin layers can be increased by a factor of 2,000 by the addition of a small concentration of ferric chloride. Whereas it may take eight minutes to clear the background of a light-sensitive lecithin element devoid of photoactivators using near ultraviolet radiation, lecithin elements containing from about 1-15 by weight ferric chloride based on the weight of the lecithin are so lightsensitive that they must be handled under yellow safety lights much like silver halide emulsions. The ferric chloride-photoactivated lecithin is about 10 times slower than silver halide printing papers but faster than commercial diazo material. Ferric chloride also advantageously in creases the toughness and integrity of phosphatide layers.

Other suitable photoactivators capable of producing free-radicals include benzil, benzoin, Michlers ketone, diacetyl, phenanthraquinone, p-dimethylaminobenzoin, 7, 8-benzofiavone, trinitrofluorenone, desoxybenzoin, 2,3- pentanedione, dibenzylketone, nitroisatin, di(6-dimethylamino-3-pyradil)methane, metal naphthanates, N-methyl- N-phenylbenzylamine, pyridil, 5-7 dichloroisatin, azodiisobutyronitrile, trinitroanisole, chlorophyll, isatin, bromoisatin, etc. These compounds can be used in a concentration of .001 to 2 times the weight of the film-forming organic material (.1%200% the weight of film former). As in most catalytic systems, the best photoactivator and optimum concentration thereof is dependent upon the film-forming organic material. Some photoactivators respond better with one type of fil'm former and may be useful over rather narrow concentration ranges whereas others are useful with substantially all film-formers in wide concentration ranges.

The acyloin and vicinal diketone photoactivators, particularly benzil and benzoin are preferred. Benzoin and benzil are effective over Wide concentration ranges with substantially all film-forming light-sensitive organic materials. Although slightly inferior to ferric chloride as photoactivators for lecithin, they are capable of increasing the light-sensitivity of the ethanol-insoluble fraction of lecithin to nearly the level of ferric chloride-sensitized lecithin. Benzoin and benzil have the additional advantage that they have a plasticizing or softening effect on filmforming light-sensitive layers, thereby increasing the powder receptivity of the light-sensitive layers. When employed as a photoactivator, benzil should preferably comprise at least 1% by weight of the film-forming organic material (.01 times the film former weight).

Dyes, optical brighteners and light absorbers can be used alone or preferably in conjunction with the aforesaid free-radical producing photoactivators (primary photoactivators) to increase the light-sensitivity of the light-sensitive layers of this invention by converting the light rays into light rays of longer lengths. For convenience, these secondary photoactivators (dyes, optical brighteners and light absorbers) are called superphotoactivators." Suitable dyes, optical brighteners and light absorbers include 4-methy1- 7 dimethylaminocoumarin, Calcofiuor yellow HEB (preparation described in US. Pat. 2,415,373), Calcofiuor white SB super 30080, Calcofiuor, Uvitex W conc., Uvitex TXS conc., Uvitex RS (described in Textil-Rundschau 8 [1953], 339), Uvitex WGS conc., Uvitex K, Uvitex CF conc., Uvitex W (described in Textil-Rundschau 8, [1953], 340), Aclarat 8678, Blancophor OS, Tenopol UNPL, MDAC S-8844, Uvinul 400, Thilfiavin TGN conc., Aniline yellowS (low conc.), Seto flavine T 5506440, Auramine 0, Calcozine yellow OX, Calcofiuor RW, Calcofiuor GAC, Acetosol yellow 2 RLS-PHF, Eosine bluish, Chinoline yelloW--P conc., Ceniline yellow S (high conc.), Anthracene blue violet fluorescence, Calcofiuor white MR, Tenopol PCR, Uvitex GS, Acid yellow-T-supra, Acetosol yellow 5 GLS, Calcocid OR. Y. Ex. conc., diphenyl brilliant flavine 7 GFF, Resofiorm fluorescent yel. 3 GPI, Eosin yellowish, Thiazole fiuoroescor G, Pyrazalone organe YB3 and National FD&C yellow. Individual superphotoactivators may respond better with one type of light-sensitive organic film-former and photoactivator than with others. Further, some photoactivators function better with certain classes of brighteners, dyes and light absorbers. For the most part, the most advantageous combinations of these materials and proportions can be determined by simple experimentation.

As indicated above, plasticizers can be used to impart optimum powder receptivity to the light-sensitive layer. With the exception of lecithin, most of the film-forming light-sensitive organic materials useful in this invention are not powder-receptive at room temperature but are powder-receptive above room temperature. Accordingly, it is desirable to add sufficient plasticizer to impart room temperature (15 to 30 C.) or ambient temperature powder receptivity to the light-sensitive layers and/or broaden the R range of the light-sensitive layers. Plasticizers are particularly useful in continuous tone reproduction systems, where the light-sensitive layer must have a R of at least 0.5 and preferably 0.7-2.0. If the R is less than 0.5, the developed image lacks the tonal contrast necessary for aesthetically pleasing continuous tone reproductions.

While various softening agents, such as dimethyl siloxanes, glycerol, vegetable oils, etc. can be used as plasticizers, benzil and benzoin are preferred since, as pointed out above, these materials have the additional advantage that they increase the light-sensitivity of the film forming organic materials. As plasticizer-photoactivators, benzoin and benzil are preferably used in a concentration of 1% to by weight of the film-forming solid organic material.

The preferred positive-acting light-sensitive film formers containing no conjugated terminal ethylenic unsaturation include the esters and acids of internally ethylenically unsaturated acids, particularly the phosphatides, rosin acids, partially hydrogenated rosin acids and the partially hydrogenated rosin esters. These materials, when compounded with suitable photoactivators, preferably acyloins or vicinal diketones together with superphotoactivators, or ferric chloride in the case of lecithin, require less than 2 minutes exposure to clear the background of light-sensitive layers and yield excellent continuous tone reproductions having a R of at least 0.5 as well as line image and half-tone reproductions.

In general, the negative-acting, light-sensitive layers useful in this invention comprise a film forming organic material in its naturally occurring or manufactured form, or a mixture of said organic material with plasticizers and/or photoactivators for adjusting powder receptivity and sensitivity to actinic radiation. Suitable negative-acting, filmforming organic materials include n-benzyl linoleamide, dilinoleyl-alpha-lecithin, castor wax (glycerol l2-hydroxystearate), a polyisobutylene, polyvinyl stearate, etc. Of these, castor wax is preferred. These materials can be compounded with plasticizers and/or photoactivators in the same manner as the positive-acting, light-sensitive, film-forming organic materials.

Surprisingly, some solid light-sensitive organic film formers can be used to prepare either positive or negativeacting, light-sensitive layers. For example, a poly(n-butyl metliacrylate) layer containing 20 percent benzoin (20 parts by weight benzoin per 100 parts by weight polymer) yields good positive-acting images. Increasing the benzoin level to 100 percent converts the poly(n-butyl methacrylate) layer into a good negative-acting system.

The light-sensitive elements useful in this invention are prepared by applying a thin layer of solid, light-sensitive film-forming organic material having a potential R of 0.2 to 2.2 (i.e. capable of developing a R or R of 0.2 to 2.2) to a suitable substrate (glass, metal, ceramic, paper, plastic, etc.) by any suitable means dictated by the nature of the material (hot-melt draw down, spray, roller coating or air knife, flow or dip coating from solvent solution, curtain coating, etc.) so as to produce a reasonably smooth homogeneous layer of from about 0.1 to 40 microns thick. The light-sensitive layer must be at least 0.1 micron thick and preferably at least 0.4 micron in order to hold suitable powders during development. If the light-sensitive layer is less than 0.1 micron, or the developing powder diameter is more than 25 times layer thickness, the light-sensitive layer does not hold powder with the tenacity necessary to form a permanent record. In general, as layer thickness increases, the light-sensitive layer is capable of holding larger particles. However, as the light-sensitive layer thickness increases, it becomes increasingly difficult to maintain film integrity during development. Accordingly, the light-sensitive layer must be from 0.1 to 40 microns, preferably from 0.4 to microns, with 0.5 to 2.5 microns being best.

The preferred method of forming light-sensitive elements of predetermined thickness entails flow coating a solution in organic solvent (hydrocarbon, such as hexane, heptane, benzene, etc.; halogenated hydrocarbon, such as chloroform, carbon tetrachloride, 1,1,l-trichloroethane, trichloroethylene, etc.) of the light-sensitive organic film former alone or together with dissolved or suspended photoactivators and/or plasticizers onto the substrate. Typically, the solution dries in air to a continuous clear film in less than one minute. As illustrated in the examples, the thickness of the light-sensitive layer can be varied as a function of the concentration of the solids dissolved in the solvent.

The substrates for the light-sensitive elements should be smooth and uniform in order to facilitate obtaining a smooth coating. While transparent supports can be employed, opaque supports, preferably white, are preferred for optimum eye appeal and/or for determining R of a light-sensitive element. Suitable substrates include metals, such as steel and aluminum plates, sheets and foils, glass, paper such as 80 lb. white Luster-kote cover CIS (coated on one side of the paper), cellulose esters, such as cellulose acetate, cellulose propionate, cellulose butyrate, etc., polyethylene terephthalate, nylon, polystyrene, polyethylene, corona discharge treated polyethylene, polypropylene, Tedlar PVF (polyvinyl fluoride), polyvinyl alcohol, amylose, etc. The supports or bases can be subbed with various hydrophobic polymers, such as cellulose acetate, cellulose butyrate, cellulose propionate, polystyrene, polyethylene terephthalate, polyethylene, polypropylene, polyvinyl fluoride, etc., or hydrophilic subbing layers such as polyvinyl alcohol, hardened gelatin, amylose, polyacrylic acid, etc., in order to provide the supports or substrates with a surface having the desired hydrophilic or hydrophobic properties. In general, it is preferred to apply a 10 subbing layer to paper substrates to slow down the penetration of organic solvent solutions, and other things being equal, facilitates the formation of thicker light-sensitive layers.

For the purposes of dye imbibition imaging, it is understood that the selection of substrate or subbing layer for the substrate is dependent upon the solubility characteristics of the particulate dye employed in the developer, i.e. the surface of the substrate should be swellable in vapors of a material which is a solvent for the dye. For example, water soluble dyes should be employed with a substrate having a hydrophilic surface such as polyvinyl alcohol, amylose, paper subbed with a hydrophilic layer such as hardened gelatin, polyvinyl alcohol, amylose, polyacrylic acid, etc. If a hydrocarbon or halohydrocarbon soluble dye is employed, the surface of the substrate should be capable of swelling in vapors of a hydrocarbon or halohydrocarbon. Generally, the hydrocarbon or halohydrocarbon soluble dyes are employed with substrates having an oleophilic surface. However, polyvinyl pyrrolidone can be used advantageously as a subbing layer to receive water soluble dyes or halohydrocarbon soluble dyes.

A latent image is formed in the light-sensitive elements of this invention by exposing the element to actinic radiation in image-receiving manner for a time suflicient to provide a potential R of 0.2 to 2.2 (clear the background of the positive-acting, light-sensitive layers or establish a potential R of 0.2 to 2.2 with negative-acting, lightsensitive layers). The light-sensitive elements can be exposed to actinic light through a photographic positive or negative, which may be line, half-tone or continuous tone, etc.

As indicated, the latent images are produced from positive-acting, light-sensitive layers by exposing the element in image-receiving manner for a time sufficient to clear the background, i.e. render the exposed areas non-powderreceptive. As explained below, the amount of actinic radiation necessary to clear the background varies to some extent with developer powder size and development conditions. Due to these variations, it is often desirable to slightly overexpose line and half-tone images in order to assure complete clearing of the background. Slightly more care is necessary in continuous-tone work since overexposure tends to decrease the tonal range of the developed image. In general, overexposure is preferred with negative-acting, light-sensitive elements in order to provide maximum contrast.

After the light-sensitive element is exposed to actinic radiation for a time sufiicient to clear the background of a positive-acting, light-sensitive layer or establish a potential R of 0.2 to 2.2, a suitable developing powder having a diameter or dimension along one axis of at least 0.3 micron is applied physically with a suitable force, preferably mechanically, to embed the powder in the lightsensitive layer. The developing powder can be virtually any shape, such as spherical, acicular, platelets, etc. Suitable deformation imaging powders include nickel flakes, aluminum flakes, molybdenum disulfide, glass beads, microethene polyethylene, Teflon spheres, montan wax, sulfur, stainless steel spheres, rice starch, pigments, solid dyes, etc. having a diameter along at least one axis of at least 0.3 micron.

Although the developing powders in deformation imaging, in general, can be a pigment or dye of suitable size, it is preferable to employ solid materials, such as resinous or polymeric materials, as carriers for pigments or dyes, since most pigments or dyes are not available in the required size range for use in this invention. For use in dye imbibition deformation imaging, a solid carrier is preferably used with the dye in order to control particle size of the developing powder and to control the intensity of the final dye image. The pigments or dyes can be ballmilled with polymeric carrier in order to coat the carrier with pigment or dye or, if desired, pigments or dyes can be blended above the melting point of a resinous carrier,

ground to a suitable size and classified. In some cases, it is advantageous to dissolve dye and carrier in a mutual solvent, dry and grind to suitable size. For dye imbibition deformation imaging, it is preferable to coat the carrier with dye, since the dye is more readily and more effectively imbibed into the substrate. If the dye is in the carrier matrix, more dye must be employed to obtain comparable brilliance and image density. Usually the developing powder contains from 0.1 to 50% by weight dye and correspondingly 99.9 to 50% by weight carrier. However, the latter route tends to preclude individual dye particles from depositing in non-image areas.

The black developing powder for determining the R of a light-sensitive layer is formed by heating about 77% Pliolite VTL (vinyltoluenebutadiene copolymer) and 23% Neo Spectra carbon black at a temperature above the melting point of the resinous carrier, blending on a rubber mill for fifteen minutes and then grinding in a Mikro-atomizer. Commercially available powders such as Xerox 914 Toner give substantially similar results although tending towards slightly lower R, values.

Suitable carriers for the dye include hydrophilic polymeric carriers such as polyvinyl alcohol, granular starch (preferably corn or rice), animal glue, gelatin, gum arabic, gum tragacanth, carboxy polymethylene, polyvinyl pyrrolidone, Carbowaxes, etc.; hydrophilic monomeric materials such as sorbitol, mannitol, dextrose, tartaric acid, urea, etc.; hydrophobic carriers, such as polystyrene, Pliolite VTL (butadiene-styrene copolymer), polymethyl methacrylate, etc.

Suitable water soluble dyes include Alphazurine 2G, Calcocid Phloxine 2G, Tartrazine, Acid Chrome blue 3BA Conc., Acid Magenta 0., Ex. Conc., Neptune Blue BRA Conc., Nigrosine, Jet Conc., Patent Blue AF, Ex. Conc., Pontacyl Light Red 4 BL Conc. 175%, etc. Suitable oil soluble dyes include Oil Blue ZV, Oil Red N-1700, etc.

As explained in our commonly assigned application Ser. No. 849,520, filed Aug. 12, 1969, now abandoned, the hydrophobic carriers, particularly those soluble in hydrocarbons and halohydrocarbons, have the advantage that they can be removed at a later stage in the processing with a suitable solvent, when employed in conjunction with the preferred halohydrocarbon or hydrocarbon light-sensitive materials. Further, dye imbibition images produced with hydrophobic carriers tend to be glossy. On the other hand, the polymeric hydrophilic carriers tend to partially dissolve and imbibe during the dye imbibition step, leading to a somewhat matte finish. Accordingly, the particular carrier employed can be varied to obtain either a glossy or matte finish. Likewise oil soluble dyes can be used with hydrophilic carriers, etc. and imbibed into the surface of substrates having a suitable surface which is oil swellable, hydrocarbon swellable or halohydrocarbon swellable, etc.

The developing powders useful in this invention contain particles having a diameter or dimension along at least one axis from 0.3 to 40 microns, preferably from 0.5 to microns with powders of the order of 1 to 7 microns being best for light-sensitive layers of 0.4 to 10 microns. Maximum particle size is dependent on the thickness of light-sensitive layer while minimum particle size is independent of layer thickness. Electron microscope studies have shown that developing powders having a diameter 25 times the thickness of the light-sensitive layer cannot be permanently embedded into light-sensitive layers and, generally speaking, best results are obtained where the diameter of the powder particle is less than about 10 times the thickness of the light-sensitive layer. For the most part, particles over 40 microns are not detrimental to image development provided the developing powder contains a reasonable concentration of powder particles under 40 microns, which are less than 25 times, and preferably less than 10 times, the light-sensitive layer thickness. However, other things being equal, the larger the developer powder particles (above 10 microns), the lower the R of the developed image. For example, when Xerox 914 Toner, classified to contain (a) all particles under 1 micron, (b) 1 to 3 micron particles, (c) 3 to 10 micron particles, (d) 10 to 18 microns, and (e) all particles over 18 microns, was used to develop positive acting 1 micron thick lecithin light-sensitive elements after the same exposure, the images had a R of (a) 0.83, (b) 0.95, (c) 0.97, (d) 0.32, and (e) 0.24, respectively.

Although particles over 40 microns are not detrimental to image development, the presence of particles under 0.3 micron diameter along all axes can be detrimental to proper image formation. In general, it is preferable to employ developing powders having substantially all powders having a diameter along at least one axis not less than 0.3 micron, preferably more than 0.5 micron, since particles less than 0.3 micron tend toembed in non-image areas. For example, mechanical development with commercial carbon blacks: .008 micron Neo Spectra Mark I, .020 micron Peerless, .025 micron Raven Bead, .041 micron Statex B, .055 micron Statex R and .073 micron Molacco all resulted in substantially equal powder embedment in image and non-image areas with a positiveacting, light-sensitive lecithin element. Substantially less background or non-image area powder embedment occurred using 0.3-0.4 micron iron oxide IRN-351, 0.4 micron iron oxide BK-247 and BK-250, 0.55 x 0.08 micron iron oxide IRN and 0.550 x 0.08 micron IRN with the same positive-acting, light-sensitive lecithin element.

As the particle size of the smallest powder in the developer increases, less exposure to actinic radiation is required to clear the background. For example, when Xerox 914 Toner, classified to contain (a) all particles under 1 micron, (b) 1 to 3 micron particles, (c) 3 to 10 micron particles, (d) 10 to 18 micron particles, and (e) over 18 micron particles, was used to develop the lightexposed portions of positive-acting 1 micron thick lecithin 1ight-sensitive elements, the exposed portions had a R of (a) 0.26, (b) 0.23, (c) 0.10, (d) 0 and (e) 0 after equal exposures. By suitably increasing the exposure time, the R of the non-image areas was reduced to substantially zero with particles (a), (b) and (c).

In general, somewhat more deposition of powder particles into non-image areas can be tolerated when using a black developing powder than a colored powder, since the human eye is less offended by gray background or non-image areas than by the deposition of colored particles in non-image areas. Therefore, the concentration of particles under 0.3 micron and the size of the developing powder is more critical when using a colored powder such as cyan, magenta or yellow. For best results, the developing powder should have substantially all particles (at least 95% by weight) over 1 micron in diameter along one axis and preferably from 1 to 7 microns for use with light-sensitive layers of from 0.4 to 10 microns. In this way, powder embedment in image areas is maximum and relatively little powder is embedded into non-image areas. Accordingly, rice starch granules, which are 5 to 6 microns, are particularly useful as carriers for dyes of different hues.

In somewhat greater detail, the developing powder is applied directly to the light-sensitive layer, while the powder receptive areas of said layer are in at most only a slightly soft deformable condition and said layer is at a temperature below the melting points of the layer and powder. The powder is distributed over the area to be developed and physically embedded into the stratum at the surface of the light-sensitive layer, preferably mechanically by force having a lateral component, such as to-and-fro and/or circular rubbing or scrubbing action using a soft pad, fine brush or even an inflated balloon. If desired, the powder may be applied separately or contained in the pad or brush. The quantity of powder is not critical provided there is an excess available beyond that required for full development of the area, as the develop ment seems to depend primarily on particle-to-particle interaction rather than brush-to-surface or pad-to-surface forces to embed a layer of powder particles substantially one particle thick (monoparticle layer) into a stratum at the surface of the light-sensitive layer. When viewed under an inverse microscope, spherical powder particles under about microns in diameter enter the powder-receptive areas first and stop dead, embedded substantially as a monolayer. The larger particles seem to travel over the embedded smaller particles which do not rotate or move as a pad or brush is moved back and forth over the developed area. Non-spherical particles, such as platelets, develop like the spherical powders except that the fiat side tends to embed. Only a single stratum of powder particles penetrates into the powder-receptive areas of the light-sensitive layer even if the light-sensitive layer is several times thicker than the developer particle diameter.

The minimum amount of powder of the preferred type required to develop an area to its maximum density is about 0.01 gram per square inch of light-sensitive surface. Ten to 20 or more times this minimum range can be used with substantially the same results, a useful range being about 0.02 to 0.2 gram per square inch.

The pad or brush used for development is critical only to the extent that it should not be so stiff as to scratch or scar the film surface when used with moderate pressure with the preferred amount of powder to develo the film. Ordinary absorbent cotton loosely compressed into a pad about the size of a baseball and weighing about 3 to 6 grams is especially suitable. The developing motion and force applied to the pad during development is not critical. A force as low as a few grams applied to the pad when using the preferred amount of powder will develop an area of the film to essentially maximum density, although a suitable material could withstand a developing force of 300 grams with substantially the same density resulting in both instances. A force of 10 to 100 grams is preferred to assure uniformity of results. A slightly longer developing time seconds) may be required at the lower loading while only a few seconds would be required at the higher loading. The speed of the swabbing action also is not critical other than that it afiects the time required; rapid movement requiring less time than slow. The preferred mechanical action involved is essentially the lateral action applied in ultrafine finishing of a wood surface by hand sanding or steel wooling.

Hand swabbing is entirely satisfactory, and when performed under the conditions described above, will reproducibly produce the maximum density which the material is capable of achieving. That is, the maximum concentration of particles per unit area will be deposited under the prescribed conditions, dependent upon the physical properties of the material such as softness, resiliency, plasticity, and cohesivity. Substantially the same results can be achieved using a mechanical device for the powder application. A rotating, or rotating and oscillating, cylindrical brush or pad may be used to provide the described brushing action and will produce a substantially similar end result.

If a substantially larger mechanical force is employed to develop positive-acting, light-sensitive layers, the solid, unexposed material together with embedded powder are removed from the substrate surface and moved to the light-exposed non-image areas forming a reversal image. It has also been found that it is possible to move the unexposed positive-acting light-sensitive layer from a grained metal substrate to the exposed portion prior to powder development. Excellent negative half-tone images have been produced by applying developer powder to the originally positive-acting system.

After the powder application, excess powder remains on the surface which has not been sufliciently embedded into, or attached to, the film. This may be removed in any convenient way, as by wiping with a clean pad or brush usually using somewhat more force than employed in mechanical development, by vacuum, by vibrating, or by air doctoring. For simplicity and uniformity of results, the excess powder usually is blown off using an air gun having an air-line pressure of about 20 to 40 p.s.i. The gun is preferably held at an angle of about 30 to 60 degrees to the surface at a distance of 1 to 12 inches (3 to 8 preferred). The pressure at which the air impinges on the surface is about 0.1 to 3, and preferably about 0.25 to 2, pounds per square inch. Air cleaning may be applied for several seconds or more until no additional loosely held particles are removed. The remaining powder should be sufiiciently adherent to resist removal by moderately forceful wiping or other reasonable abrasive action. If a resinous binder is used in the formulation of the developing powder, scuff resistance can be improved after removing excess powder by brief (2 to 5 seconds) exposure of the specimen to heat or to solvent vapors to fuse the resin. When dye imbibition deformation imaging is employed, heat or solvent fusion of resinous carrier can be employed after the dye imbibition step.

Under some circumstances, it is possible to develop an image Without applying mechanical force, such as by using air pressure or cascade-development techniques, which use large carrier beads as a driving force. However, the image is usually imperfect in the sence that it has lower contrast and the image areas lack uniformity or proper tonal values, when compared to images developed using the prescribed mechanical force. For example, when a light-sensitive Staybelite resin element, capable of yielding a R of 1.9 with the aforementioned preferred black toner (77% Pliolite VTL23% Neo Spectra carbon black) at room temperature using mechanical force, was dusted at room temperature with the preferred black toner and subjected to air pressure (a non-mechanical, physical force), such as that normally used to remove excess powder particles from non-image areas, a non-uniform image was obtained having a maximum R of 0.67. The non-uniform image was similar to images developed with insufficient developer using mechanical force. When the non-uniform air-developed element was gently swabbed with a clean cotton pad, image uniformity improved somewhat. When the same light-sensitive Staybelite resin element, capable of yielding a R of 0.99 with Xerox 914 Toner at room temperature using mechanical force, was developed by cascade development at room temperature using Xerox 914 Toner with large carrier beads as a driving force, air cleaned and wiped with a cotton pad, an image having a R of 0.66 was obtained. Although this image lacked the excellent resolution and uniformity of images developed using mechanical force, it had substantially better image qualities than images developed using air pressure alone or air pressure followed by gentle wiping. While air pressure or cascade development have been used with some success with light-sensitive Staybelite resin elements, not all lightsensitive elements of this invention can be developed in this manner. Attempts to develop light-sensitive lecithin elements using air pressure or cascade development at room temperature have generally resulted in images having a R of less than 0.2.

The reflection density, and the R in particular, of a light-sensitive layer is also dependent upon the temperature of the light-sensitive layer during physical embedment. In general, the higher the temperature of the light-sensitive layer, the higher the R of the developed image. For example, Staybelite Ester No. 10 alone, which is incapable of forming an image having a R of at least 0.2 from 0-130" F. can be developed to a R of about 0.2 at F. and about 0.6 at F. Similarly, soybean lecithin, in its naturally occurring form, which readily develops a R of about 0.7 to 0.9 with a suitable developer at room temperature, yields a R of less than 0.2 at 0 F.

To some extent reproducibility of results and length of exposure are also dependent upon the relative humidity of the development chamber or area. For development at higher relative humidity, sensitized-lecithin elements must be exposed to more actinic radiation to clear the background. For example, other things being equal, an exposed lecithin element, which is non-powder receptive at 38% RH. (relative humidity) has a background R of 0.16 at 48% RH, 0.38 at 56% RH. and 0.61 at 65% RH. On the other hand, rosin derivatives, such as Staybelite Ester No. 10, are much less sensitive to relative humidity.

As indicated above, powder particles comprising a dye, held in image-wise configuration in particulate form in or on a substrate can be molecularly dispersed and imbibed into the surface of the. substrate by treating the image with vapors of a material which is a solvent for said dye and capable of swelling the surface of the substrate. The process of molecularly imbibing particulate dye into the substrate converts the dye particles, in particulate form, into a molecularly dispersed form providing an aesthetically more pleasing saturated image. Other things being equal, the particulate dye image changes from a pale color to a brilliant, saturated, more pleasing hue.

In a typical situation, substrates bearing a hydrophilic subbing layer, such as hardened gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid, amylose, etc. are employed as dye imbibition receiving layers for water soluble dye. A suitable solid, positive-acting or negativeacting light-sensitive layer is applied to the hydrophilic subbing layer, exposed to actinic radiation in image-receiving manner to form a latent image and developed with developer particles of at least 0.3 micron along at least one axis containing a water soluble dye. At this Point, the dye component of the powder particles is separated from the hydrophilic subbing layer or receiving layer by the light-sensitive layer which may be considered as an additional subbing layer. An aesthetically, more. pleasing image is then produced by treating the developed image with vapors of a material, wherein said material is a solvent for said dye, capable of swelling the surface of said substrate and capable of transporting said dye through the original light-sensitive layer, thereby transferring the previously particulately dispersed dye to the hydrophilic subbing layer in molecularly dispersed form. For example, if the dye is water-soluble, it can be transferred to the hydrophilic subbing layer by water vapor, aqueous alcohol, etc. Essentially the same results can be obtained using a hydrophobic subbing layer such as polystyrene, polyvinylidene chloride, etc., a hydrophobic dye and suitable solvent vapors, such as hydrocarbon and halohydrocarbon vapors.

The particular solvent employed in the dye imbibition step is also dependent on the physical properties of the exposed light-sensitive layer. Although the transportation of the dye through the solid, organic layer is not completely understood, it is believed that in most cases dye imbibition is due to weakening of the light-sensitive layer by the powder particles employed during deformation imaging creating potential points of stress in the film surface. Subsequently, when solvent vapors, capable of swelling the surface of the substrate (dye imbibition receiving layer) upon which the stressed film is disposed, swell the surface of the substrate, a second stress is placed upon the light-sensitive layer due to the swelling of the receiving layer with the result that the light-sensitive layer fractures and the dye is transported through the light-sensitive layer and imbibed into the surface of the substrate. In other cases dye imbibition may be due to the solvent vapors diifusing the dissolved dye into the light-sensitive layer. In any event, the solvent must be capable of transporting the dye through the original light-sensitive layer.

Experiments have shown that the development of various light-sensitive elements, such as Staybelite Ester No. 10 and Staybelite resin, with developing powder weakens the film layer. For example, when these light-sensitive elements are developed with undyed developing powder, it is possible to imbibe water soluble dye into the receiving layer in imagewise configuration by merely dipping the developed light-sensitive element into an aqueous dye bath. In such case the water soluble dye enters the hydrophilic receiving layer in the areas defined by the undyed powder particles. Accordingly, in such case, it is clear that transportation of the dye through the lightsensitive layer is at least partially due to weakening of the light-sensitive layer by developer particle.

It has also been found that the above light-sensitive materials have a tendency to puddle up in the exposed areas in image-wise configuration when merely exposed to light and treated with water vapors. Accordingly, dye imbibition of water-soluble dyes through these materials is also partially due to the ability of moist warm air to disrupt the unexposed areas of the light-sensitive layer. In other cases, such as in the case of phosphatide lightsensitive elements, the exposed areas of the light-sensitive layer are converted into a more water-soluble condition than the unexposed areas as explained in copending application, Ser. No. 796,841 of Hayes, filed Feb. 5, 1969. In such case, water vapor tends to transport the dye through the exposed areas of the light-sensitive element with the result that the original positive powder image changes into a negative dye imbibition image. In still other cases, it has been possible to prevent passage of water soluble dye into the dye imbibition receiving layer by adding various hydrophobic agents, such as silicone oils in a concentration of 200 parts per million to various light-sensitive layers, such as those based on Staybelite resins and esters. The silicone tends to act as a waterproofing agent in this environment and no dye imbibition with water vapor is possible since water vapor is incapable of transporting the dye through the lightsensitive layer. Dye imbibition of water-soluble dye through light-sensitive layers based on poly(n-butyl methacrylate) and other high molecular weight hydrophobic polymers, is relatively diflicult due to the extreme hydrophobic nature of these film formers. Accordingly, routine experimentation may be carried out to determine which solvents are best for transporting specific dyes through particular light-sensitive elements.

The following examples are merely illustrative and should not be construed as limiting the scope of this invention.

- EXAMPLE I One gram Staybelite Ester No. 10 (partially hydro-- genated rosin ester of glycerol), 0.22 gram benzil and 0.30 gram 4-methyl-7-dimethylaminocoumarin, dissolved in milliliters Chlorothene (1,1,1-trichloroethane) was applied to the gelatin side of an 11" x 14" hardened gelatin coated paper by flowing the solution over the substrate supported at about a 60 angle with the horizontal. After air drying for approximately one minute, the light-sensitive layer was approximately 2.0 to 2.25 microns thick. The light-sensitive layer was placed in a vacuum frame in contact with 5 representative transparencies, as identified below. After exposure to a mercury point light source for about 60 seconds, the exposed light-sensitive element was removed from the vacuum frame and developed in a room maintained at 75 F. and 37% relative humidity by rubbing a cotton pad containing approximately 5 grams of a 77% by weight Pliolite VTL (vinyltoluene-butadiene copolymer) and 23% Neo Spectra carbon black toner, prepared in the manner described below, across the element. The black developing powder was embedded into the unexposed areas of the light-sensitive layer by rubbing the lightly compressed absorbent cotton pad about the size of a baseball weighing about 3 to 6 grams back and forth over the light-sensitive layer using essentially the same force used in ultrafine finishing of wood surface by hand sanding or steel wooling. The excess powder was removed from the light-sensitive layer by impinging air at an angle of about 30 to the surface until the surface was substantially free of unembedded particles. The reproduction was then wiped with a fresh cotton pad resulting in excellent resolution and faithful reproduction of the transparencies. The scanning electron microscope showed that a monolayer of particles was embedded in the image areas. The developed reproduction was then placed in a chamber containing trichloroethylene vapors maintained at room temperature for about seconds to fuse the powder particles to the light-sensitive layer.

The transparencies used in this example included (1) a l33-line-per-inch-half-tone transparency containing boxes A to H and J to M, whose light transmission varies from 9.7% to 85.1%, located across the top of the lightsensitive element, (2) an 85-line-per-inch-positive halftone transparency of a young girl positioned to the left under the 133 line per inch half-tone transparency, (3) a Stoufrer No. 1 continuous-tone resolution guide bearing steps numbered from 1 to 21 positioned to the right under the 133 line per inch half-tone transparency, (4) a 120-line-per-inch-half-tone and 6-to-10 point type positive transparency in the lower left hand corner and (5) a continuous-tone positive transparency of a womans head and shoulders in the lower right hand corner.

The percent light transmission of the half-tone areas of the 133-line-per-inch-half-tone transparency and R of the developed half-tone areas are set forth below in Table I.

TABLE I Percent light Reflection transmission of density (Rd) of Box No transparency reproduction The percent light transmission of the Stoufier No. 1 continuous-tone resolution guide and R of the developed image areas are set forth below in Table II.

TAB LE II Percent light Reflection transmission of density of Numbered steps transparency reproduction The R of the developed continuous-tone reproduction of the woman ranged from 0.08 in the forehead area to 1.2 in the shadow tone.

The black developing powder used in the example and employed for determining the R of light-sensitive layers was prepared by heating a mixture of about 77% by weight Pliolite VTL (vinyltoluene-butadiene copolymer) and 23% by weight Neo Spectra carbon black to 350 F. to produce a pliable mixture, mixing on a rubber mill for minutes, cooling to room temperature, and then grinding in a Mikro-atomizer. Over 99% by Weight of the particles in the toner were between about 2 to 40 microns as measured by a Coulter Counter. Approximately 28% by weight of the powder particles were from about 2 to 10 18 microns with an additional 22% by weight from 10 to 15 microns.

The above example clearly shows that excellent continuous-tone, half-tone and line images can be produced by the method of this invention.

EXAMPLE II Example I was repeated using a ninety second exposure and developed with (1) Statex B carbon black having an 0.041 micron average particle size in place of the Pliolite VTL-carbon black toner and (2) black iron oxide IRN- 351 having a 0.3 to 0.4 micron average particle size in place of the Pliolite VTL-carbon black toner.

The Statex B carbon black embedded into both image and non-image areas resulting in dark black images on a black background. The dots in the 133-line per-inch-halftone could not be distinguished with the naked eye due to the dark background. In some cases, the shadow tones (half-tone boxes A to G) were visible since they developed blacker or shinier than the background areas while in other cases the most exposed areas (face of the woman prepared from the continuous-tone positive) was apparent only by virtue of the higher gloss in the most light-exposed areas as compared to a duller black in the least exposed areas. The Stouffer resolution guide gave additional anomalous results with steps 1 to 3 having essentially the same blackness as the background areas, steps 4 to 6 a very dark appearance due to the high gloss in these steps and steps 7 to 21 having a duller black than steps 4 to 6.

For the most part, the black iron oxide was embedded almostly solely into the unexposed areas. Although the light irradiated background areas had a light gray cast, it was possible to distinguish the individual dots in each of boxes A to H and J to M of the 133-1ine-per-inch-halftone. Seven steps on the Stouffer chart were distinguishable with the naked eye. The continuous-tone image of the woman did not develop properly since the length of exposure was insuflicient to harden the light exposed areas sufiiciently to resist embedment of particles of this small size. If exposed for a longer length of time a continuoustone reproduction is formed.

The above example clearly shows that particles having a diameter along at least one axis of at least 0.3 micron are suitable for use in the process of this invention.

EXAMPLE III Five grams of the ethanol-insoluble fraction of soybean lecithtin, 1.5 gramsbenzil and 0.05 gram 4-methyl-7-dimethylaminocoumarin, dissolved in ml. C C1 was flow coated over Lustercoat paper and air-dried to form a 1.5 micron light-sensitive layer. The light-sensitive element was used to copy a translucent engineering drawing by passing the light-sensitive element through a Bruning Copyflex Model 250 at No. 10 setting equipped with a mercury lamp rated at 100 Watts per inch. At this speed setting, which is normally used for medium speed diazos, the exposure time was about 5 to 6 seconds. An excellent black and white copy was formed by embedding the Pliolite VTL-Neo Spectra carbon black toner described in Example I in the manner described in Example I.

The light-sensitive element described in this example formed excellent continuous-tone reproductions by (l) exposing through a continuous-tone positive for 2 /2 minutes using a sunlamp as the light source and (2) exposing through a continuous-tone positive for 30 seconds using a sunlamp as the light source, followed by heating the exposed element in an oven at C. for three minutes and cooling to room temperature prior to powder embedment.

EXAMPLE IV This example illustrates the use of the light-sensitive element of Example HI in a complex lens system. Line subjects were reproduced using the light emitted from a 750- watt projector. The light was projected through a slide transparency through a lens onto a mirror about 3 feet in front of the projector that reflected the imagedownward about 2 feet focusing on the lecithin coated lightsensitive layer. After'exposure for about 5 minutes and heating at 150 C. in an oven for 4 minutes and cooling to room temperature, an excellent line image was formed using the developer powder described in Example I in the manner described in Example I.

EXAMPLE V Five grams of the ethanol-insoluble fraction of soybean lecithin and 0.2 gram benzil, dissolved in 100 ml. carbon tetrachloride was flow coated over Lustercoat paper and air dried. The light-sensitive element was used to reproduce a continuous-tone image from a continuous-tone transparency by passing the light-sensitive element through the Brunning Copyflex copier described in Example III at No. 3 speed setting. At this speed setting, which is normally used for slow speed diazos, the exposure time was about seconds. An excellent continuoustone black and white reproduction was formed by embedding the Pliolite VTL-Neo Spectra carbon black toner described in Example I in the manner described in Ex ample I. 1

EXAMPLE VI This example illustrates the production of an engineering drawing using the Bruning Copyflex copier described in Example III at its fastest setting. Twenty grams of unfractionated, substantially oil-free soybean lecithin and 2 grams ferric chloride in 200 ml. carbon tetrachloride were mixed for seconds with ultrasonic agitation, centrifuged, and 100 m1. decanted. A portion of the decanted liquid was flow coated on Lustercoat paper in the manner described in Example III. The light-sensitive element was used to copy a translucent engineering drawing by passing the light-sensitive element through the Bruning Copyflex copier at No. 40 setting. At this speed setting, exposure time was about one second. An excellent, slightly overexposed black and white copy was formed by embedding the Pliolite VTL-Neo Spectra carbon black toner in the manner described in Example III. The reproduction was slightly overexposed due to the limited speed of the copier, which was only designed to accommodate the use of commercial diazo products.

EXAMPLE VII Five grams of unfractionated, substantially oil-free soybean lecithin and .5 gram ferric chloride in 100 ml. Chlorothene was dispersed by an ultrasonic tool for one mini ute, filtered through Celite Super cell and flow coated on Lustercoat paper in the manner described in Example III. An image was projected on the light-sensitive element by placing the National Bureau of Standards microcopy resolution chart slide in a ml. projector equipped with a SOD-watt projection bulb. The image was projected onto the lecithin coated paper for 90 seconds and developed with Xerox 914 Toner to yield an excellent enlargement 7 times thatof the original.

When the National Bureau of Standards transparency was placed in contact with the light-sensitive lecithin element on a glass plate and exposed to an arc lamp for 30 seconds, an excellent contact print resolving 60 line pairs per mm. was developed with Xerox Toner.

EXAMPLE VIII This example illustrates the use of the light-sensitive element of Example VII in the production of reflex copies. The light-sensitive element of Example VII was placed in contact with a printed page with the printed side in contact with the light-sensitive lecithin layer. The backside of the light-sensitive element was exposed to a fluorescent lamp for approximately one minute. The image 20 was developed in the manner described in Example III yielding an'excellent mirror line image.

EXAMPLE IX This example illustrates that the thickness of flow coated light-sensitive layers of this invention can be controlled by controlling the solids in the light-sensitive coating since layer thickness increases as total solids in the coating composition increases.

Six hundred-twenty-five-one thousandths of a gram of Staybelite resin (partially hydrogenated rosin acids), .05 gram benzil, and .156 gram 4-methyl-7-dimethylaminocoumarin, dissolved in ml. Chlorothene was applied to the gelatin side of hardened gelatin coated paper, to aluminum foil and to gelatin coated glass by flowing the solution over the substrate supported at about a 60 angle with the horizontal. The thickness of the light-sensitive coatings was determined by weight-difference (weighing the substrate before and after coating) or by sectioning the central portion of the coated light-sensitive element. The light-sensitive layer was 0.55 micron on gelatin coated glass by sectioning, 0.59 micron on gelatin coated glass by weight-difference, 0.65 micron on aluminum foil by weight-difference and 0.75 micron on the gelatin coated paper by sectioning.

One and one-quarter grams Staybelite resin, .1 gram benzil and .3125 gram 4-methyl-7-dimethylaminocoumarin, dissolver in 100 ml. Chlorothene was applied to aluminum foil in the above described manner and yielded a 2.25 micron light-sensitive layer by weight-difference. Two and one-half grams Staybelite resin, .2 gram benzil and .625 gram 4-methyl-7-dimethylaminocoumarin, dissolved in 100 ml. Chlorothene was flow coated on hardened gelatin coated paper yielding a 4.3 micron light-sensitive layer by sectioning.

Five grams Staybelite resin, .4 gram benzil and 1.25 grams 4-methyl-7-dimethylaminocoumarin, dissolved in 100 ml. Chlorothene was flow coated on aluminum foil and on steel foil. The light-sensitive layer was 6.25 microns by weight-ditference on aluminum foil and 6.04 microns by sectioning on steel foil. 7

Each of the light-sensitive layers was exposed to ligh through a positive continuous-tone transparency and developed with the developing powder of Example I in the manner described therein to yield excellent positive continuous-tone images.

EXAMPLE X On'eand one-fourth grams Staybelite Ester No. 5 (partially hydrogenated rosin ester of glycerol), .1875 gram benzil and .3125 gram 4-methyl-7-dimethylaminocoumarin, dissolved in 100 ml. Chlorothene was flow coated on the gelatin side of a hardened gelatin coated paper, exposed to a fluorescent lamp through a continuous-tone positive transparency and developed in the manner described in Example I to form an excellent continuoustone positive reproduction.

EXAMPLE XI One and one-fourth grams Staybelite resin F (partially hydrogenated rosin acids), .1 gram benzil and .3125 gram 4-methyl-7-dimethylarninocoumarin, dissolved in 100 ml. Chlorothene was flow coated on the gelatin side of hardened gelatin coated paper, exposed to a fluorescent lamp through a continuous-tonepositive'transparency and developed in the manner described in Example I to form an excellent continuous-tone positive'reproduction.

EXAMPLE XII One and one-fourth grams wood resin, .15 gram benzil and .3125 gram"4-methyl-7-dimethylaminocoumarin, dissolved in 100 ml. Chlorothene was flow coated on the gelatin side of hardened gelatin coated paper, exposed to a fluorescent lamp through a continuous-tone positive transparency and developed in the manner described in 21 Example I to form an excellent continuous-tone positive reproduction.

EXAMPLE XIII One and one-fourth grams abietic acid, .15 gram benzil and .3125 gram 4-methyl-7-dimethylaminocoumarin, dissolved in 100 ml. Chlorothene was flow coated on the gelatin side of a hardened gelatin coated paper, exposed to a fluorescent lamp through a continuous-tone positive and developed in the manner described in Example I to yield an excellent continuous-tone positive reproduction.

EXAMPLE XIV This example illustrates the preparation of continuoustone and half-tone reproductions using a negative-acting light-sensitive material of this invention. Eight-tenths gram Castorwax F-l (hydrogenated castor oil), 0.2 gram benzil and 0.2 gram 4-methyl-7-dimethylaminocournarin, dissolved in 100 ml. Chlorothene was flow coated on the gelatin side of a hardened gelatin coated paper. The lightsensitive layer was placed in a vacuum frame in contact with continuous-tone negatives and an SS-Iine-per-inch negative half-tone transparency. After exposure to a 100- amp carbon arc lamp for approximately 80 seconds, the exposed light-sensitive element was developed with the black developing powder, in the manner described in Example I to form continuous-tone positive and half-tone positive of the respective negative transparencies. The developed reproductions were then placed in a chamber containing trichloroethylene vapors maintained at room temperature for about 5 seconds to fuse the powder particles to the light-sensitive layer.

EXAMPLE XV One and one-quarter gram Chlorowax 70 LMP, .3 gram benzil and .3125 gram 4-rnethyl-7-dimethylaminocoumarin, dissolved in 100 ml. Chlorothene was flow coated on the gelatin side of a hardened gelatin coated paper, exposed to light through a continuous-tone positive transparency and developed in the manner described in Example I with the Pliolite VTL-Neo Spectra carbon black toner to form an excellent continuous-tone positive reproduction. This sensitized system is roughly equivalent to various rosin esters, acids and hydrogenated rosin acids and esters.

EXAMPLE XVI Five grams of Piccotex (alpha-methyl styrene-vinyltoluene copolymer having a ball and ring softening print of 75 C.) and one gram benzil, dissolved in 100 ml. Chlorothene was flow coated on a grained aluminum plate. The light-sensitive layer was placed in a vacuum frame in contact with a continuous-tone positive transparency, an 85 line-per-inch positive halftone transparency and positive line transparency. After exposure for minutes to a 100 ampere arc lamp at a distance of 48 inches, the light-sensitive element was developed with the Pliolite VTL-carbon black toner in the manner described in Example I to form positive continuous, half-tone and line reproductions. The light source was maintained at 48 inches in order to avoid heating the light-sensitive layer which tends to become too tacky when warmed slightly.

EXAMPLE XVII Seven grams Cumar VI (para-coumarone-indene resin), 3 grams Hercolyn D (hydrogenated methyl ester of rosin), 3 grams benzil and 1 gram 4-methyl-7-dimethylaminocoumarin were flow coated on a grained aluminum plate. The light-sensitive layer was placed in contact with a continuous-tone positive transparency. After exposure to a sunlamp for about 5 minutes, the exposed light-sensitive element was developed in the manner described in Example I to form a continuous-tone positive image.

EXAMPLE XVIII This example illustrates an attempt to use the polymerizable composition described in Example I of US. Patent 3,060,024 in the manner described in Example I of said patent and in accordance with the present invention. An initial preparation of polyethylene terephthalate/sebacate was prepared using a procedure based on that described by Sorenson and Campbell in Preparation Methods of Polymer Chemistry, Interscience Publishers, Inc., New York (1961) pp. 113-4 for the preparation of polyethylene terephthalate. Fifteen grams (0.08 mole) of dimethyl terephthalate, 18 grams (0.08 m.) dimethyl sebacate, 24 grams (0.39 m.) ethylene glycol, 0.05 gram calcium acetate hydrate, and 0.12 gram of antimony trioxide were placed in a flask. The flask was immersed and kept for 3 hours in a 197 C. metal bath while a slow stream of nitrogen was passed through a capillary tube which reached to the bottom of the flask. The bath temperature was raised to 222 C. for 20 minutes and then to 283 C. for 2 hours. The nitrogen flow was discontinued at this point. The polymerization was continued for five hours at about 0.3 mm. pressure. The resulting product had the consistency of a thick syrup.

A coating solution was prepared according to Example I of the patent containing 15 grams polyethylene terephthalate/sebacate, 83.3 cc. dichloromethane, 2.7 grams tetraethylene glycol diacrylate, 0.003 gram phenanthraquinone and 0.003 gram p-methoxyphenol. This coating solution was quite fluid and was flow coated on a 3-mil Mylar substrate yielding a layer between .5 and 1 mil which was very soft and greasy. The coatings were much too soft to place in contact with transparencies in a vacuum frame.

A coating on 3-mil Mylar was exposed to ultraviolet light through a metal stencil mask held out of contact from the coating for a prolonged period and heated on a hot plate at C. resulting in liquefaction of the unexposed areas. Five micron aluminum powder platelets having a diameter along one axis of from 0.8 to 15 microns was dusted over the surface and the specimen was allowed to cool. The aluminum powder was wiped off the light-irradiated areas leaving a heavy multilayer deposit of particles frozen into the unexposed areas. Although the polymerizable layer was not as thick as described in Example I of the patent, the unexposed material became quite fluid at the dusting-on temperature, and a heavy multi-layer deposit of aluminum platelets was obtained.

Since the above light-sensitive layer could not be used in contact with a transparency in a vacuum frame, a second preparation of polyethylene terephthalate/sebacate was made by essentially the same procedure except that 0.12 mole of dimethyl terephthalate and 0.06 mole of dimethyl sebacate was used. A coating solution was prepared using the polyethylene terephthalate/sebacate as described in Example I. A film deposited from this solution on Mylar was dry to the touch. Cotton-swab development of the unexposed layer at room temperature using mechanical force with the same aluminum platelets produced a smooth reflective image, which was substantially a monolayer of the aluminum platelet particles. Although this material was not quite as fluid at 120 C. as the product made with the first batch of polyethylene terephthalate/ sebacate, dusting-on at 120 C. resulted in a rough multilayer deposit. Attempts to image this light-sensitive element in a vacuum frame using an arc lamp gave only a faint hint of where the transparency had been but no recognizable image.

A continuous-tone reproduction was produced with the light-sensitive composition described in the preceding paragraph by adding 20% by weight benzil to the coating composition based on the weight of the polyethylene terephthalate/sebacate. The composition was flow coated onto grained aluminum, placed in contact with a continuoustone positive and exposed to a sunlamp for 15 minutes. The light-sensitive element was developed with mechanical force using titanium dioxide in the manner described in Example I yielding a continuous-tone positive image which was inferior to those described in the preceding examples. Heating the plate to 120 C. prior to development and dusting on titanium dioxide destroyed the continuous tone effect.

EXAMPLE XIX A coating solution was prepared according to Example I of U.S. Pat. 3,060,024 using terephthalate/sebacate (prepared from 0.12 mole dimethyl terephthlate and 0.06 mole dimethyl sebacate), 1.5 grams benzil, and 0.01 gram 4-methyl-7-dimethylaminocoumarin Was flow-coated on grained aluminum and air dried. Two sections of the coated aluminum sheet were similarly exposed for 15 minutes to a sunlamp through the same continuous-tone positive transparency. One light exposed section was placed on a hot plate set at 150 C., titanium dioxide was sprinkled over the entire surface, cooled to room temperature, and excess titanium dioxide removed. The result was a harsh differential between areas of particle retention and particle rejection with no intermediate areas of particle retention corresponding to intermediate degrees of light exposure. The other exposed section was developed with titanium dioxide at room temperature using the prescribed mechanical application of swabbing with a cotton pad resulting in similar extremes in powder retention to the dusting on technique but also producing the many intermediate degrees of powder receptivity between these extremes in proportion to the degree of light exposure.

EXAMPLE XX This example illustrates how the room temperature reflection density of the methylol amide of Example II of application Ser. No. 643,367 varies with the concentration of glycerol in the coating composition. A solution of the methylol amide of Example II was applied to a glass substrate. The light-sensitive layer had a R of at room temperature. With the addition of (1) 0.2 gram, (2) 0.4 gram, (3) 0.6 gram, (4) 0.8 gram, (5) 1.0 gram and (6) 1.2 grams of glycerol per 10 cc. of coating solution, the room temperature R using Xerox 914 Toner was respectively (1) 0.8, (2) 1.0, (3) 1.5, (4) 1.7, (5) 1.85 and (6) 2.0. These layers were sensitive to ultraviolet light radiation and the background could be cleared by suitable exposure.

EXAMPLE XXI Five grams polyethylmethacrylate and 2.5 grams benzoin, dissolved in 350 ml. methylethyl ketone was flow coated on gelatin coated paper, exposed to light through a metal mask for 20 seconds and developed in the manner described in Example I using Xerox 914 Toner to form a positive image.

EXAMPLE XXII Five grams poly (n-butylmethacrylate and 5 grams benzoin, dissolved in 690 ml. methylethyl ketone was flow coated on gelatin coated paper, exposed to light through a metal mask for 20 seconds and developed in the manner described in Example I using Xerox 914 Toner to form a negative image.

When this example was repeated using 5 grams poly(nbutylmethacrylate) and 2.5 grams benzoin dissolved in 375 ml. methylethyl ketone, a positive image was formed.

EXAMPLE XXIII This example illustrates the relationship between the thickness of the light-sensitive layer and diameter of developer particles. A series of lecithin solutions comprising from 0.5 gram to 50 grams of substantially oil-free soybean lecithin in 100 ml. of chlorothene were fiow coated on glass and air dried. The layer thickness was determined by sectioning the glass coated with solutions containing at least 5 grams lecithin and extrapolating the thickness of solutions containing less than 5 grams lecithin.

The data is set forth below in Table III.

Spherical glass beads of known uniform size [(1) 9 to 17 microns, (2) 17 to 24 microns, (3) 24 to 26 microns, (4) 26 to 30 microns and (5) 53 to microns] were spread generously over the lecithin elements and a loaded rubber roller was moved over the glass beads in order to embed the particles through particle-to-particle contact. The excess beads were blown off with an air stream in the manner described in Example I. Photomicrographs were made of each area at x magnification. The monoparticles embedment of the glass beads was apparent under each condition for which the beads remained attached to the film. The larger beads remained embedded in the thicker layers only, with the number of beads embedded per unit area being directly proportional to layer thickness; the smaller beads showed the same proportional relationship :0 layer thickness, but remained attached to the thinner ayers.

None of the 53 to 74 micron beads remained embedded in the layers of less than one micron thickness although cavities were apparent in the lecithin layer where beads were pressed into the layer but were subsequently blown off by the air. Approximately half the surface of the 1 micron layer was coveredby beads of 9'to 17 microns, a few 17 to 24 micron beads were embedded and only scattered larger beads were embedded. Higher concentration of beads remained in the layers of increasing thickness. The 9 to 17 micron beads and the 17 to 24 micron beads were packed about as closely as possible as a monolayer in the 5 to 6 micron layer. The 24 to 26 micron and '26 to 30 micron beads were fairly closely packed in the 5 to 6 micron layer and approximately half of the 5 to 6 micron layer was covered by the 53 to 74 micron beads. The above data clearly shows that the maximum particle size that can be embedded in any layer van'es with layer thickness.

EXAMPLE XXIV Granular rice starch, which is uniformly 5 to 6 microns, was applied to the soybean lecithin layers of from /8 to 5 to 6 microns thickness described in Example XXIII using a cotton pad in the manner described in Example I. Rice starch was embedded in negligible amounts in the micron layer, in scattered areas of the less than 0.25 micron layer, about 50% of the more than 0.25 micron layer, about 75% of the approximately one micron layer and closely packed in the 2 and 5 to 6 micron layers. Based on data in Examples XXIII and XXIV, the developer part cle must have a diameter along one axis less than 25 times the light-sensitive layer thickness in order to be embedded in the light-sensitive layer. 1

EXAMPLE XXV The light-sensitive soybean lecithin element described in Example III was exposed to a sunlamp through a metal mask, developed with stainless steel spheres having a range of from 1 to 60 microns (number average of 13 microns) using a cotton pad in the manner described in Example I to form a positive image.

25 The same results were obtained using micronized irregular polygonal coke particles of 1 to microns as the developing powder.

EXAMPLE XXVI This example illustrates the screening of a number of free radical progenitors as photoactivators for light-sensitive lecithin compositions. Five grams of the ethanol insoluble residue of soybean lecithin and from .1 to .2 gram of free radical progenitor, dissolved in 100 ml. carbon tetrachloride were flow coated on Lustercoat paper in the manner described in Example III. A metal mask was positioned over the light-sensitive element and individual areas were exposed to 1, 2, 4, and 8 minutes. The results are set forth below in Table IV. The photoactivators rated A had a pronounced effect on the light sensitivity of the lecithin layer. Those ranked B made a definite improvement, although not nearly as much under the conditions of evaluation as those rated A. Many of the materials rated C had some effect on light-sensitivity but were considerably less efiective than those rating A and B.

TABLE IV Sensitizer: Rating Benzil A Benzoin A Michlers ketone A Diacetyl A Phenanthraquinone A p-Dimethylaminobenzoin A 7-8-benzoflavone A Nitroisatin A Di(6-dimethylamino-3-pyradil)methane A Trinitrofluorenone A Metal naphthanates B Dimethylaniline B Desoxy benzoin B 2,3-pentanedione B Chlorophyll in oil B Dibenzylketone B N-methyl-N-phenylbenzylamine B Pyridil B 5-7 dichloroisatin B Azodiisobutyronitrile B Tripiridyl-S-triazine B Trinitroanisole B Oil soluble chlorophyll B 'Isatin B Bromoisatin B Chloranil C 2-(p-iodophenyl) 3-(p-nitrophenyl) 5 tetrazolium chloride C p-Nitrobenzene diazoniumfluoborate C Trans 1,2 dibenzylethylene C Tertiary butylhydroperoxide C Benzoinoxime C Ninhydrin C S-methylisatin C Benzylhydrol C N-benzylideneaniline C Tetrazolium violet C p-Tolyltetrazolium chloride C TPTC Formazan C E-tolyl TC Formazan C Hexanitra-diphenylamine C Dithiobis-2(2-nitrobenzoic acid) C Tetraphenyl-boron sodium C 4 hydroxy-2-butanone C N-benzylpiperidinium methiodide C Anthracene C N,N-dirnethy1aniline C Iron dicyclopentadienyl C Lead tetraacetate C Glyoxal C EXAMPLE XXVII This example illustrates the development of colored reproductions using a polymeric material as a carrier for a hydrophilic dye in dye imbibition imaging. One and one-quarter grams Staybelite Ester No. 10, .25 gram benzil and .25 gram 4-methyl-7-dimethylaminocoumarin, dissolved in ml. Chlorothene was applied to the gelatin side of a hardened gelatin coated paper by flow coating the solution over a substrate supported at about a 60 angle with the horizontal. After air drying for approximately one minute, the light-sensitive layer was approximately 2.25 to 2.50 microns thick. The light-sensitive element was placed in a vacuum frame in contact with continuous tone, half-tone and line transparencies in the manner described in Example I and exposed to a carbon are for about 60 seconds. The light-sensitive element was removed from the vacuum frame and developed in a room maintained at 75 F. and 37% relative humidity by rubbing a cotton pad containing an Alphazurine 2G (cyan) polyvinyl alcohol toner of from 1 to 10 microns diameter along the largest axis, prepared in the manner described below across the element. The cyan developing powder was embedded into the unexposed areas of the lightsensitive layer by rubbing the loosely compressed absorbent cotton pad about the size of a baseball weighing about 3 to 6 grams back and forth over the light-sensitive layer using essentially the same force used in ultrafine finishing of wood surfaces by sanding or steel wooling. The excess powder was removed from the light-sensitive layer by impinging air at an angle of about 30 to the surface until the surface was substantially free of particles. The reproduction wasthen wiped with a fresh cotton pad resulting in excellent continuous tone, half-tone and line reproductions of the positive transparencies. The Scanning electron microscope showed that a monolayer of particles was embedded in the image areas. The developed image was placed over a beaker of boiling water for about 15 seconds during which time the pale blue dye image was imbibed and molecularly dispersed in continuous tone configuration into the hardened gelatin layer. The molecularly dispersed image changed from a pale blue to a brilliant, saturated aesthetically more pleasing cyan hue.

The toner employed in this example was prepared by tumbling one part by weight of cyan with 10 parts by weight polyvinyl alcohol fines with porcelain balls for 15 minutes.

Essentially the same results are obtained by replacing the Staybelite Ester No. 10 light-sensitive element with the Staybelite Ester No. 5 element of Example 10, the Staybelite resin F element of Example 11, the wood rosin light-sensitive element of Example 12 and the abietic acid light-sensitive element of Example 13.

Essentially the same results are obtained by replacing the hardened gelatin coated paper with polyvinyl alcohol subbed paper and polyvinyl pyrrolidone subbed paper.

EXAMPLE XXVIII Example XXVII was repeated using a toner prepared by forming a 1 to 3% by weight Alphazurine 2G solution in methanol, adding from 20 to 50 grams polyvinyl alcohol (ground to 1 to 10 microns diameter along at least one axis) per 100 grams alcoholic solution, agitating for from about 2 to 18 hours, filtering drying and then tumbling for about 15 minutes to break up the agglomerates. The dye imbibition image was not quite as brilliant or intense as the imbibed image prepared in Example XXVI since less dye was imbibed into the hydrophilic subbing layer. More dye was retained within the polyvinyl alcohol matrix. However, this reproduction was substantially more brilliant and more intense than the image prepared in Example XXVII prior to dye imbibition.

27 EXAMPLE XXIX Example XXVII was repeated with essentially the same results replacing the Alphazurine 2G dye in the toner with the same weight concentration of Calcocid Phloxine (magenta). The molecularly dispersed dye imbibition image was markedly more brilliant than the embedded image prior to dye imbibition.

EIMMPLE XXX Example XXVII was repeated with essentially the same results replacing the Alphazurine 2G dye in'the toner with the same weight concentration of Tartrazine (yellow). The molecularly dispersed dye imbibition image was markedly more brilliant than the embedded image prior to dye imbibition.

EXAMPLE XXXI Example XXVII was repeated with essentially the same results replacing the polyvinyl alcohol in the toner with carboxy polymethylene (Carbapol 940 and 941), gelatin and animal glue on an equal basis.

EXAMPLE XXXII This example illustrates the use of a hydrophobic resinous. material as a carrier for the hydrophilic dye in dye imbibition transfer. One and one-quarter grams Staybelite resin, 0.1 gram benzil and .3125 gram 4-methyl- 7-dimethylaminocoumarin, dissolved in 100 ml. Chlorothene was applied to gelatin coated paper in the manner described in Example XXVII to form a 2.25 micron light-sensitive layer. The light-sensitive layer was exposed to light through a continuous-tone positive transparency in the manner described in Example XXVII and developed with an Alphazurine 2G-Pliolite VTL toner, described below, in the manner described in Example XXVII. The excellent continuous-tone pale blue reproduction was imbibed and molecularly dispersed in the gelatin layer by holding the embedded reproduction over boiling water for seconds. The reproduction changed from a pale blue to a brilliant saturated cyan hue. Photomicrographs of the powder embedded image before and after dye imbibition showed 1) that the lightsensitive layer puddled up when contacted with steam, (2) 90% of the embedded particles did not move during steaming, and (3) about 10% of the particles, those havingthe least surface area per volume (largest particles) moved slightly.

The Alphazurine 2G-1Pliolite VTL toner was prepared by milling 200 grams of micronized Pliolite VTL and grams Alphazurine 26 on a ball mill with porcelain balls for 64 hours.

Essentiallythe same results were obtained by replacing the Pliolite VTL in the toner with Piccolastic D125 (styrene polymer) and polyisobutyl methacrylate.

A slightly less intense cyan image is obtained by replacing the cyan toner used in this example with a cyan toner prepared by fusing the Alphazurine 2G with Pliolite VTL in the manner used to prepare the black toner of Example I. When a cyan toner prepared by fusing 30 parts by weight Alphazurine 2G and 80 parts Pliolite VTL in the manner described in Example I was used in place of the cyan toner used in this example, a dye imbibed image of comparable intensity was formed.

EXAMPLE XXXIII Example XXXII was repeated with essentially the same results using a light-sensitive coating composition consisting of 0.6 gram Staybelite Ester No. 10, 0.2 gram Pliolite VTL, 0.21 gram benzil, and 0.15 4-methyl-7- dimethylaminocoumarin.

Essentially the same results are obtained using hot moist air.

EXAMPLE XXXIV This example illustrates the use of lPliolite VTL as the sole film forming component of a light-sensitive'ele- EXAMPLE XXXV Example 32 was repeated with essentially the same results replacing the Pliolite VTL in the toner with'5 to 6 micron rice starch granules and with l2-microi1 corn starch granules The principal difference was that the cyan image developed with corn starch was somewhat more saturated than the rice starch image.

EXAMPLE XXXVI This example illustrate dye imbibition of a hydrophobic dye into a hydrophobic subbing layer. Baryta paper bearing a /3 mil polyethylene subbing layer was flow coated with a composition consisting of 1.25 grams Staybelite resin, 0.10 gram benzil, and 0.316 gram 4-methyl- 7-dimethylaminocoumarin, dissolved in 100 ml. Chlorothene. The light-sensitive element was exposed through a metal stencil mask for 60 seconds to a 275 watt sunlamp and developed with'rice starch bearing an oil-soluble blue dye in the manner described in Example XXVII. The element was placed in a chamber of saturatedChlorothene vapors at room temperature for about 20 seconds molecularly imbibing the dye particles into the polyethylene layer.

The developing powder used in this example was pre pared by blending 0.2 gram American Cyanamid Oil Blue ZV and 1.80 grams rice starch suspended in Chlorothene, evaporating to dryness on a hot plate at 50 C., and grinding with a mortar and pestle.

Essentially the same results were obtained replacing the blue dye in the developing powder with 0.2 gram American Cyanamid Oil Red N-1700'.

EXAMPLE XXXVII A sheet of white, lb. Lusterkote Cover CIS paper bearing a polyvinyl alcohol subbing layer was flow coated with a solution of 1.5 gram Paricin l5 (ethylene glycol monohydroxy' stearate), 0.2 gram benzil and 0.2 gram 4-methyl-7-dimethylaminocoumarin dissolved in mls. Chlorothene. Thelight-sensitive element was placed in a vacuum frame in contact with a yellow half-tone negative color transparency, exposed for about 5 seconds to a mercury light source and developed in the manner described in Example I, except that the powder particles were embedded into the exposed areas of the lightsensitive layer. After the non-embedded particles were removed, the yellow dye was molecularly imbibed into the polyvinyl alcohol subbing layer by holding the element over boiling water for 15 seconds. The molecularly dispersed image changed from a pale yellow to a brilliant, saturated, aesthetically pleasing yellow hue.

'EXAMPLE XXXVIII This example illustrates the use of Chlorowax as a lightsensitive film former in dye imbibition imaging. One gram Chlorowax 7O LMP (chlorinated paraffin), .45 gram benzil and .25 gram 4-methyl-7-dimethylaminocoumarin, dissolved in-lOO mls. Chlorothene, was applied to gelatin coated paper in the manner described in Example 27,

exposed to light through a continuous-tone positive transparency in the manner described in Example 27, and developed with an Alphazurine 2G- Pliolite VTL toner described in Example 32. The excellent continuous-tone pale blue reproduction was imbibed and molecularly dispersed in the gelatin layer by holding the embedded reproduction over boiling Water for 15 seconds. The reproduction ghanged from a pale blue to a brilliant, saturated cyan 29 EXAMPLE XXXIX Example 38 was repeated using a light-sensitive element composed of one gram Piccotex 75 (alpha-methyl styrene-vinyltoluene copolymer) and .2 gram benzil dissolved in 100 mls. Chlorothene. After exposure of ten minutes in a 100-ampere arc lamp, the light-sensitive element was developed in the manner described in Example 38 and the cyan dye was molecularly dispersed into the gelatin coated paper in the manner described in Example 38.

When this example was repeated adding .15 gram 4- methyl-7-dimethyl-aminocoumarin to the light-sensitive solution, the exposure time was reduced to one minute.

EXAMPLE XL Example 38 was repeated with essentially the same results using a light-sensitive solution comprising 100 milliliters of Chlorothene, .8 gram Dimerex (resin dimer), .6 gram benzil and .6 gram 4-methyl-7-dimethylaminocoumarin, and a four minute exposure.

While this invention is directed primarily to a method of forming dye imbibition continuous-tone, line and halftone images, wherein powder particles comprising a dye, embedded in image-Wise configuration in a stratum at the surface of a powder receptive, solid, organic layer supported on a substrate, is molecularly imbibed into the substrate by contacting the particles embedded in said organic layer with vapors of a material, which is a solvent for said dye and capable of swelling the surface of said substrate, the present invention can be used to prepare line or half-tone dye imbibition images by contacting powder particles comprising a dye, held in image-wise configuration in particulate form in or on a substrate, with vapors of a material, which is a solvent for said dye and capable of swelling the surface of said substrate, molecularly imbibing said dye into said substrate. In other words, the present invention is not limited to dye imbibition deformation imaging. Numerous other less advantageous imaging techniques can be used to deposit dye particles in or on the substrate prior to the dye imbibition step. For example, a powdered dye image can be deposited on a suitable substrate using a stencil, by typing from a ribbon containing dye particles, by stratum transfer of a dye developed image prepared in the manner described in US. Pat. 3,060,024, by xerographic technique, etc. In some of these processes, the dye can be deposited with or without using a solid carrier for the dye. In others, particularly xerographic processes, the dye must be in or on a suitable solid carrier.

The present invention can be used xerographically, for example, by uniformly charging a substrate bearing a photoconductor, such as zinc oxide dispersed in a hydrophilic binder (polyacrylic acid), exposing to light in image-receiving manner discharging the charge in the exposed areas, depositing a suitable charged solid toner comprising a solid carrier and a dye (preferably a water soluble dye), and then contacting said solid toner with vapors of a material (water), which is a solvent for said dye and a swelling agent for the surface of said substrate, molecularly imbibing said dye into the substrate. If desired, the triboelectrically charged powder image containing dye can be transferred from a selenium plate to a suitable substrate prior to dye imbibition.

Since many embodiments of this invention may be made and since many changes may be made in the embodients described, the foregoing is to be interpreted as illustrative only and our invention is defined by the claims appended hereafter.

What is claimed is:

1. The process for forming dye imbibition deformation images which comprises:

(1) exposing to actinic radiation in image-receiving manner a substrate bearing a solid, positive-acting. light-sensitive organic layer having a thickness of 30 from 0.1 to 10 microns, said layer being capable of developing a R of 0.2 to 2.2;

(2) continuing the exposure to clear the background of the light-sensitive layer whereby the most exposed areas are rendered non-poWder-receptive;

(3) applying to said layer of organic material, freeflowing powder particles having a diameter, along at least one axis, of at least about 0.3 micron but less than 25 times the thickness of said organic layer whereby said powder particles comprise a solid carrier and dye;

(4) while the layer is in at most a slightly soft deformable condition and is at a temperature below the melting point of the powder, mechanically embedding said powder particles as a monolayer in a stratum at the surface of said light-sensitive layer whereby said powder particles displace at least a portion of the light-sensitive layer to yield an image having portions varying in density in proportion to the exposure of each portion;

(5) removing non-embedded particles from said organic layer to develop an image; and

(6) transporting said dye through said solid, organic layer molecularly imbibing said dye into said substrate by contacting the particles embedded in said organic layer with vapors of a material, which is a solvent for said dye, capable of swelling said substrate and capable of transporting said dye through said solid, organic layer.

2. The process of claim 1, wherein the substrate comprises a base bearing a hydrophilic subbing layer and the dye is water soluble.

3. The process of claim 1, wherein the vapors of a material, Which is a solvent for said dye and capable of swelling the surface of said substrate, comprises water.

4. The process of claim 1, wherein the dye is on the surface of said solid carrier.

5. The process of claim 1, wherein the dye is within the solid carrier matrix.

6. The process of claim 1, wherein said substrate comprises a base bearing a hydrophobic subbing layer.

7. The process for forming dye imbibition deformation images which comprises:

( 1) exposing to actinic radition in image-receiving manner a substrate bearing a solid, negative-acting, lightsensitive organic layer having a thickness of from 0.1 to 10 microns, said layer being capable of developing a R of 0.2 to 2.2;

(2) continuing the exposure to establish a R of 0.2 to 2.2 in the exposed areas whereby powder will adhere to the most exposed areas;

(3) applying to said layer of organic material, freefiowing powder particles having a diameter, along at least one axis, of at least about 0.3 micron but less than 25 times the thickness of said organic layer whereby said powder particles comprise a solid carrier and dye;

(4) while the layer is in at most a slightly soft deformable condition and is at a temperature below the melting point of the powder, mechanically embedding said powder particles as a monolayer in a stratum at the surface of said light-sensitive layer whereby said powder particles displace at least a portion of the light-sensitive layer to yield an image having portions varying in density in proportion to the exposure of each portion;

(5) removing non-embedded particles from said organic layer to develop an image; and

(6) transporting said dye through said solid, organic layer molecularly imbibing said dye into said substrate by contacting the particles embedded in said organic layer with vapors of a material, which is a solvent for said dye, capable of swelling said substrate and capable of transporting said dye through said solid, organic layer.

8. The process of claim 7, wherein said substrate comprises a base bearing a hydrophilic subbing layer and said dye is water soluble.

9. The process of claim 8, wherein the vapors'of a material, which is a solvent-for said dye and capable of swelling the surface of said substrate, comprises water.

10. The process of claim 2, wherein said base comprises paper. I

11. The process of claim 10, wherein said paper base bears a subbing layer selected from the group consisting of hardened gelatin and polyvinyl alcohol.

' 12. The process of claim 3, wherein the carrier for said dye comprises a vinyltoluene-butadiene copolymer.

13. The process for forming dye'imbibition deformation images which comprises:

"(1) exposing toactinic radiation in image-receiving manner a substrate bearing a solid, positive-acting, light-sensitive organic layer having a thickness of from 0.1 to 10 microns, comprising a film-forming organic material containing no terminal ethylenic unsaturation and at least one photoactivator selected from the group consisting of primary photoactivators capable of producing free radicals and superphotoactivators capable of converting light rays into light rays of longer lengths, said layer being capable of developing a R of 0.4 to 2.0 at room temperature;

(2) continuing the exposure to clear the background of the light-sensitive layer whereby the most-exposed areas are rendered non-powder-receptive;

(3) applying to said layer of organic material, freeflowing powder particles having a diameter along at least one axis of at least about 0.3 micron but less than 25 times the thickness of said organic layer;

(4) while the layer is in at most a slightly soft deformable condition and is at a temperature below the melting point of the powder, mechanically embedding said powder particles as a monolayer in a stratum at the surface of said light-sensitive layer whereby said powder particles displace at least a portion of the light-sensitive layer to yield an image having portions varying in density in proportion to the exposure of each portion; 1

(5) removing non-embedded particles from said organic layer to develop an image; and

(6) transporting saiddye through said solid, organic layer, molecularly imbibing said dye into said substrate, by contracting the particles embedded in said organic layer with vapors of a material which is a solvent for said dye, capable. of swelling said substrate and capable of transporting said dye through said solid, organic layer.

14. The process of claim 13, whereinsaid light-sensitive layer is at room temperature in Step 4.

15. The process .of claim 13, wherein said substrate comprises a base bearing a hydrophilic subbing layer,.said dye is water soluble and said solvent for said dye comprises water.

16. The process of claim 15, wherein said solid film forming organic material comprises an internally ethylenically unsaturated acid.

17. The process of claim 16, wherein said solid, filmforming organic material comprises a partially hydrogenated rosin acid.

18. The process of claim 15, wherein said solid, filmforming organic material comprises an ester of an inter: nally ethylenically unsaturated acid.

19. The process of claim 18, wherein said ester comprises a partially hydrogenated rosin ester.

20. The process of claim 15, wherein said film-forming organic material comprises a polymer of an ethylenically unsaturated monomer.

21. The process of claim 20, wherein said polymer comprises a copolymer of vinyltoluene and alpha methyl styrene.

22. The process of claim 15, wherein said solid, filmforming organic material-comprises a coal tar resin.

23. The process of claim 15, wherein said solid, filmforming organic material comprises a halogenated hydrocarbon.

24. The process of claim 23, wherein said halogenated hydrocarbon comprises a halogenated wax. 1

References Cited UNITED STATES PATENTS 2/1942 Whitehead 8-14 1/1971 Tanno et a1. 117,- 63

I. TRAVIS BROWN, PrimaryExaininerj A. T. SURO PICO, Assistant Examiner UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,721,561 Dated March 20, 1973 Inirentofls) Rexford' W. Jones and William B. Thompson It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

' lines 30-31; for "at. least 0.3" read-"at least'about O.3---

' Column 1,

Column 1, line 32; for "wheren" read- ---wherein-'-- Column 2 line 4; for "developing" read ---developed---' Column 2, line 10; for "photographc" read ---photographic--- Column 2, line 18; for "at" read ---a--- Column 2, line 22; for "thremoplastic" read ---thermoplastic-- Column 2, line 37; for "proceses" read ---processes--- Column 3, line 12; for "embodiment" read --embedment---' Column 3, line 56; for "than" read ---that--- Column 3, line 61; for "wel" read --well--- Column 4, line 56; for "beter" read --better--- Column 5, line 53; for "maner" read ---manner--- Y Column 10, line 59; for "microethene" read --microthene--- Column 14, line 26; for "sence" read ---sense--- Column 18, line 31; for "almostly" read ---almost--- Column 20, line 28; for "dissolver" read --dissolved- 7 Column 23, line 55'; for "poly (n-butylmethacrylate" read ---poly (n-butylmethacrylate) Signed and sealed this 9th day of April 1971 (SEAL) Attes t:

EDWARD I-'I.FLETCHER,JR. c, MARSHALL DANN Attesting Officer Commissioner of Patents FORM PO-IOSO (10-55) USCOMM-DC 60376-P69 U. 5. GOVERNMENT PRINTING OFFICE: I965 0-366-334 

